In the United States almost 10% of the population will be diagnosed with symptomatic knee osteoarthritis by 60 years of age and knee osteoarthritis accounts for over 600,000 total knee arthroplasties per year. Yet, a treatment to modify osteoarthritis remain elusive and clinical trials are impeded by suboptimal structural outcome measures that are slow to change or limited to only one of many structural changes that occur during osteoarthritis progression. The instrument development component of this project is aimed at developing and validating a quantitative knee osteoarthritis severity outcome measure and software tool that is sensitive to change and can be applied to a knee magnetic resonance imaging in a rapid and efficient manner. Candidate features whose combination will be evaluated in this composite instrument are a whole-knee cartilage damage index, bone marrow lesion volume, and effusion volume. We will evaluate the reliability, construct and discriminative validity, sensitivity to change, and time to perform the measurements in datasets available from the Osteoarthritis Initiative and a clinical trial of intra-articular corticosteroids (IACS). The scientific questions that we will test to assess validity of this instrument are (1) whether knees subject to a new injury exhibit accelerated rate of progression (2, exploratory) OA knees treated with IACS exhibit reduced structural progression.